The 60 GHz band is an unlicensed band which features a large amount of bandwidth and a large worldwide availability overlap. The large bandwidth means that a very high volume of information can be transmitted wirelessly. As a result, multiple applications, each requiring transmission of large amounts of data, can be developed to allow wireless communication around the 60 GHz band. Examples for such applications include, but are not limited to, wireless high definition TV (HDTV), wireless docking stations, wireless Gigabit Ethernet, and many others.
In order to facilitate such applications there is a need to develop integrated circuits (ICs) such as amplifiers, mixers, radio frequency (RF) analog circuits, and active antennas that operate in the 60 GHz frequency range. An RF system typically comprises active and passive modules. The active modules (e.g., a phased array antenna) require control and power signals for their operation, which are not required by passive modules (e.g., filters). The various modules are fabricated and packaged as radio frequency integrated circuits (RFICs) that can be assembled on a printed circuit board (PCB). The size of the RFIC package may range from several to a few hundred square millimeters.
In the consumer electronics market, the design of electronic devices, and thus the design of RF modules integrated therein, should meet the constraints of minimum cost, size, power consumption, and weight. The design of the RF modules should also take into consideration the current assembled configuration of electronic devices, and particularly handheld devices, such as laptop and tablet computers, in order to enable efficient transmission and reception of millimeter wave signals. Furthermore, the design of the RF module should account for minimal power loss of receive and transmit RF signals and for maximum radio coverage.
Operations in the 60 GHz band allow the use of smaller antennas as compared to lower frequencies. However, as compared to operating in lower frequencies, radio waves around the 60 GHz band have high atmospheric attenuation and are subject to higher levels of absorption by atmospheric gases, rain, objects, etc., resulting in higher free space loss. Additionally, radio waves around the 60 GHz band are often reflected by environmental objects. These reflections can change the polarity of the transmissions and this change varies depending on the direction of the polarity of the transmission, as the reflection coefficients for various polarization directions can differ.
This sensitivity to environmental conditions makes determining a link path important. The link path describes the path the radio wave takes between the transmitter and receiver. The link path may include multiple paths such as direct line of sight (LOS), reflection, diffraction, scattering and others. Unlike a radio link in lower frequencies, in a 60 GHz link, reflections are the second dominant mode, right after LOS. Other modes occur significantly less frequently and are rarely selected. Determining whether a LOS connection is desirable because many wireless devices need a way to estimate the distance between a transmitter and receiver. The connection mode influences this measurement because an indirect path may result in a longer measured distance than the actual distance.
Existing techniques for determining the distance include time-of-flight (TOF), estimations of the power-delay-profile (PDP), received power level, and in-room mapping. While these techniques may be sufficient for devices operating in frequencies lower than about seven GHz, these techniques alone are insufficient for transmissions around the 60 GHz band. For example, for the 60 GHz band, the PDP of a reflected path can be similar to that of a non-reflective path. Therefore, a technique for determining whether there is a LOS or non-LOS connection is desired.